The present invention relates to a method for controlling shifting actions of a motor vehicle having an internal combustion engine and an automatic transmission, wherein intermediate gas is automatically applied when downshifting.
With automatic transmissions, shifting pressures which occur during downshifting processes affect the driving comfort, the life span of the transmission and, in particular, with a very engaged method of driving with high transverse accelerations, the driving stability of the vehicle.
It is known in the state of the art to apply intermediate gas automatically for reducing and/or compensating the abrupt shift during a downshifting process. During this shifting process, the speed of the engine is increased to the speed that is required by the transmission after the downshifting process.
It is disadvantageous with the known methods for reducing or compensating the abrupt shift, that downshifting processes can only be perceived in an acoustically insufficient manner. This disadvantage can be observed particularly with very quiet engines.
One object of the invention, therefore is to provide an improved method for reducing or compensating an abrupt downshifting process. The improved method shall in particular depict downshifting processes in an acoustically clear manner.
This and other objects and advantages are achieved by the method according to the invention, in which intermediate gas is automatically applied for reducing or compensating for an abrupt downshift. In a first phase, in which the transmission is in its hydraulic down time, the actual torque provided by the engine is thereby slowly increased, until a torque required by the transmission is achieved. (This first phase is also called filling phase or slow start-up of the engine). Subsequently, a throttle valve is opened further in a second phase, in which the actual torque provided by the engine is still smaller than a target torque of the engine. (This second phase is also called first regulation phase and serves for the synchronization). This second phase aims for a build-up of the actual torque delivered by the engine as fast as possible in the interest of a fast shifting process; that is, the target torque of the engine is especially large (preferably at its maximum). In order to enable a build-up of the torque as fast as possible, a torque reserve is required during the second phase, which is also called reserve parameter.
According to the invention, a late ignition time is subsequently set in a third phase, which serves for the synchronization as the second phase and in which the actual torque of the engine achieves the target torque required for the synchronization. This means that the ignition angle is substantially retarded. In particular in the third phase, the ignition time is set at least intermittently later than with a crankshaft angle of +5° before the top of dead center, and in a particularly preferred embodiment, its ignition time is set after the top of dead center (for example, with a crankshaft angle of)−10°. By this strong displacement of the ignition angle, that is, the ignition time in the retarded direction, an acoustically clearly perceivable sound, in particular a very sporty sound, is generated by the engine. In order to generate this sporty sound, an additional torque reserve is required, whereby the displacement of the ignition angle, that is, the ignition time in the retarded direction, is achieved. It is also possible to blank the injection for one or several cylinders in the third phase.
Sporty characteristics of the vehicle can be emphasized acoustically by the method according to the invention. The acoustically clearly perceivable sound, in particular a very sporty sound, can thereby be differentiated in a simple manner for different driving programs of a vehicle or for different vehicle classes.
In one embodiment of the invention, one or more cylinders of the engine are blanked in a fourth phase. (That is, the ignition and/or injection of fuel are switched off completely.) In the fourth phase, (also called the trailing phase), the engine speed is synchronized, and the engine must be brought either to a torque given by the driver of the vehicle, (driver parameter torque), or to the throttle cutoff as quickly as possible. The setting of the torque of the engine as quickly as possible preferably takes place via an ignition path.
By the blanking of one or several cylinders, a sound that can be clearly perceived can be generated, in particular a very sporty sound. By means of the blanking of one or several cylinders, a reduction of the torque of the engine increased by the automatic intermediate gas to the speed required for the synchronization can in particular take place. It is thus possible to correct an additional measure of the intermediate gas which only took place for sound generation, to the measure necessary for synchronization. By switching off the ignition, it is additionally possible to generate defined explosions of a fuel air mixture in the exhaust with sufficiently high temperatures, and thereby to improve further the acoustic perceptibility of the sound during the intermediate gas.
In a further embodiment of the invention, the engine is operated in the first phase with an adjustable minimum torque, if the torque required by the transmission is smaller than the minimum torque.
Another arrangement of the method according to the invention provides that a late ignition time is set in the third phase and/or one or several cylinders of the engine are blanked in the fourth phase, only if no reserve requirement is present from the automatic transmission, a direct transmission access is present, and a required transmission torque is larger than the desired torque predefined by the driver.
With the method according to the invention, the speed of the engine required for the synchronization is automatically calculated from a measured wheel speed and a predefined target transmission.
The blanking of one or more cylinders also takes place automatically in dependence on the speed and gear when approaching the speed of the engine to the desired synchronization speed. A “bubbling” is thereby generated at the end of the shift process.
With the method according to the invention, a maximum torque reserve of the engine is calculated which is weighted with predefinable characteristic fields. The height of the torque reserve of the engine, or the position of the ignition angle (that is, the ignition time), is defined via these weightings.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.